<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">

        姓名{{username}}
        年龄{{userage}}
    </div>
    
</body>

<script>

    function  Vue(options){

        this.target = document.querySelector(options.el);

        this.target.innerHTML = this.target.innerHTML.replace("{{username}}",options.data.username);
        this.target.innerHTML = this.target.innerHTML.replace("{{userage}}",options.data.userage);


    }

    new Vue({
        el:"#app",
        data:{
            username:"leson",
            userage:18,
        }
    })

    let username  = "leson";

    let str = `${username}`


</script>
</html>